1. Field of the Invention
This invention relates to the field of multiphase alternators operating at varying speeds, and more particularly, to alternators required to have low cut-in speed combined with high current output at high speed.
2. Prior Art
Increasing power demands on automobile alternators are already pushing present day alternators toward their maximum output point and the trend for the future indicates an ever increasing power demand. A typical alternator in current use would have a cut-in speed of around 1000 rpm and supply a maximum of around 60 amperes at 8000 rpm. Increasing the size of wire used in the stator winding would increase the available current output, but because the space in the stator slots is limited if the overall size of the alternator is not changed, this would require a reduction in the number of turns in the winding, thus raising the cut-in speed. Since cut-in speed denotes that speed at which the alternator takes from the battery the function of supplying current and recharging of the battery can begin, merely increasing the wire diameter is not a desirable solution. Another approach to achieving the desired output characteristic is to use conventional windings but switch the interconnection thereof from a series to a parallel arrangement, but this method has an added complication in the sensing and switching mechanisms required. Another solution would be a larger alternator with appropriately higher cost, and since space in the engine compartment is already at a premium, this too, is not a desirable solution.